The term “hot-tapping”, as used herein, generally refers to methods for joining a first pipe to a second pipe containing or conveying a fluid without draining the fluid inside the second pipe.
Various “hot-tapping” methods for joining a connecting pipe to an existing pipe are known. Such “hot-tapping” methods are particularly useful in situations where it is desirable or necessary to join the connecting pipe to the existing pipe without stopping the flow of and/or draining the fluid inside the existing pipe. Such a connection method is particularly important when flow in the existing pipe is regulated for various downstream purposes.
Some attempts have been made at providing apparatuses and methods for “hot-tapping” pipes.
For example, PCT application publication number WO 03/002902, which is incorporated herein by reference in its entirety, describes a method and an apparatus for establishing a connection point in a pipeline containing fluid under pressure. The apparatus includes a mounting device for mounting the apparatus on a pipeline, an inner pipe that is inserted into a transition section of the mounting device, and a valve and a borer connected to one end of the inner pipe. The apparatus further includes a pretensioning device for pretensioning a seal located at the other end of the inner pipe against the pipeline. The method includes assembling the device on the pipeline, pretensioning the seal, conducting pressure tests, penetrating the pipeline with the borer, partly withdrawing the borer, closing the valve, and completely withdrawing the borer. The method may include additional steps, such as blanking or creating further pipeline connections.
In another example, U.S. Pat. No. 4,680,848 to Goldner, which is incorporated herein by reference in its entirety, describes a pipe tapping machine for cutting a hole in a pressurized main pipe wall. In use, the pipe tapping machine is mounted to a branch pipe, which is held against the main pipe wall using a removable clamp. The machine is described as including a valved port for conducting leak testing of the branch pipe prior to cutting and for venting the fluid after a hole is cut.
In yet another example, U.S. Pat. No. 6,012,878 to Hicks, which is incorporated herein by reference in its entirety, describes an apparatus and method for tapping a pressurized pipe-line located underwater. The tapping apparatus described in the reference includes means for equalizing the interior pressure of the boring bar housing to match the internal pressure of a pipeline being penetrated as an opening in the pipeline is cut by a rotating circular cutter.
However, these prior art apparatuses and methods described above are primarily directed to tapping pipes of smaller diameters and cannot be readily implemented for “hot-tapping” large diameter pipes. Typically, for such large diameter pipes, a conventional connection method is followed, which involves diverting or stopping the flow of fluid through a section of the existing pipe, draining the section of the existing pipe of fluid, and then joining the connecting pipe to the drained section of the existing pipe. As discussed above, stopping the flow of fluid in such large diameter pipes can significantly impact the operation of the facilities being serviced by these pipes. Further, it is often difficult and/or costly to install temporary piping for diverting the flow of fluid due to the volume and pressure of the fluid being carried by most large diameter pipes.
Accordingly, there exists a need for an improved method for joining a connecting pipe to an existing pipe containing fluid without disrupting the flow of fluid in the existing pipe.